Automatic toll telephone system



Aug. -19, 1952 P. BAKKER 2,607,854

AUTOMATIC TOLL TELEPHONE SYSTEM .0 v ,v 64 mm 3 26 I I 332 3 B mo I380343M 35 3 ,vggs 344A? 354 1366 TOLL LINE CIR. 250

I LINE (:IR 30 m fil- ,DIST. 388 TANDEM OFFICE 4 I --ILINE CIR I I 385FINDER coNNE ToR LINK II I %II N TONE RESTRICTED SERV. 390 300 -LY x m iv :1 r- 4 LINE CIR. =J b: 387 I 386 I I 3 39h I I I T INVENTOR.

Pler Bokker FIG. 3 By I I Attorneys Aug. 19, 1952 P. BAKKER 2,607,854

AUTOMATIC TOLL TELEPHONE SYSTEM Filed July 22, 1947 14 Sheets-Sheet 446E1EC47| 415 R3446 46l 43l- I 144 TONE 047 C482 ToLL LINE CIR. 250 R4404641 I i C4831 SEIZE igl Rlzv. R450 BAT R420 R445 START +145 TIMER fglsz MQT5LQ4I3 4 3 C428 f AUX. TONE sT.,c4|4 42s 424 4|- C I C427 TIMER425 I TANDEM OFFICE 30 i 'C47| 04m INVENTOR. FIG. 4 Pier Bokker Aug. 19,1952 Filed July 22, 1947 P. BAKKER 2,607,854

AUTOMATIC TOLL TELEPHONE SYSTEM 14 Sheets-Sheet 5 CONTROL 49% I 57lREPEATER 8x TR'UNK SEL. 4I "\.582

500 SGI L H801 1 I l-3,593 (\1 m g? i W I INVENTOR.

Pier Bokker FIG. 5 BY Attorneys Aug. 19, 1952 P. BAKKER 2,607,854

AUTOMATIC TOLL TELEPHONE SYSTEM Filed July 22, 1947 14 Sheets-Sheet '7TRUNK LINE (1771.700

FIG 7 RING bowN SUB OFFICE 40 I280 LINE cm. 770

INVENTOR. Pier Bokker Aug. 19, 1952 P. BAKKER 2,607,854

AUTOMATIC TCLL TELEPHONE SYSTEM Filed July 22, 1947 14 Sheets-Sheet 8C80lmes i 8|? s31 86l M868 0869 N362 C837 1 4 863 mm;

- c802 me ,841 8424 822 ,How ?Ms43 MARG A: R830 SIMPLEX 32 tige m andDIAL @516 5 CONTROL L imM LB R MO R860 M312 4 TIME RLS. \F 835 t 8l4 836H: EHOLD pl TRUNK CIR. 100 840 7 s00 Disir'lbuior 883 SUB OFFICE 40Finder Connector Link Inc. Conn. Y 884 885 g E E 882 21* INVENTOR. 8Pier Bokker BY M 064% M Attorneys Aug. 19, 1952 BAKKER 2,607,854

AUTOMATIC TOLL TELEPHONE SYSTEM Filed July 22, 1947 14 Sheets-Sheet 9rC97l T5 R9l 931 '1 932 964 r T I 2 r6912 (TONE 963 {G973 IIISEIZE II!R920 A 9 965 922 4 .H 3930 {F O Q13 START/94] t3 0934 93s 1 AUX. TONEST.

L 942 MOT. ST.

991 fifilggg ,2 954 4 m TIMER R950 E 'U 700 C9391 E 970 ill Z SUB OFFICE40 C 66 J; '5 F 2; O Q c991 INVENTOR. FlG. 9 Pier Bokker Attorneys Aug.19,1952 i P. BAKKER 5 AUTOMATIC TOLL TELEPHONE SYSTEM v Filed July 22,1947' 14 Sheets-Sheet 1s SUB OFFICE 40 I380 v smell LINE " TRUNK cm.\200 J R1320 l7! --\3e2 3 1- l363 Q m5 FE JI/ 1 1531 c1324 ST i 7 1 13322 R DIAL R|36O \343/\ l R1330 1 13 l B SE'ZE TIMER Li JV v Cl3l6 M351 1r 7 1 H3370 HOLD p J amt 1 E550 3 2 \352 INVENTDR.

F|G Q I Pier Bokker BY E Aug. 19,1952 P. BAKKER 2,607,854

AUTOMATIC TQLL TELEPHONE SYSTEM INVENTOR. Pier Bukker n I z z 2 PatentedAug. 19, 1952 AUTOMATIC TOLL TELEPHONE SYSTEM Pier Bakker, Chicago,Ill., assignor-toAutoma'tic Electric Laboratories, Inc.,'- Chicago,;Ill.,-a corporation of Delaware Application July 22, 1947, Serial No.762,715

r l The present invention relates to telephone systems and moreparticularly'to community automatic exchange (C'. A. X) networks.

In a C. A. 'X network, there is frequently pr vided a toll ofliceincluding a switchboard, a tandem oflice of the automatic type, andasuboffice of the automatic type; whereby traffic between the switchboardin the toll oilice and the subscriber substations in the sub-oflice mustbe trunked through the tandem office. Also the tandem ofiice frequentlycomprises restricted service features preventing some of the subscribersubstations therein from completing connections directly to subscribersubstations in the sub-office, without the aid of the operator at theswitchboard in the toll oflice.

It is a general object of the present invention to provide in a C. AJXnetwork of the character described, improved switching apparatus forsetting up the various connections between the different ofiices in asimple and eflicient manner without sacrificing supervision orcomplicating the directory number plan.

Another object of the invention is to provide in'a telephone system ofthe type noted, an improved trunk selector-digit sender andrepeatertrunk selector arrangement in which first automatic switchingapparatus is responsive to a given digit to select either therepeater-trunk selector or the trunk selector-digit senderdepending'upon trafiic conditions; whereupon the selected repeater-trunkselector selects an idle trunkline extending to the desired destination,or' the selected trunk selector-digit sender selects an I idle trunkextending to second automatic switching apparatus and then operates thesecond switching apparatus to select an idle trunk line extending to thedesired destination.

A further object of the invention is to provide in a telephone system ofthe type noted,including a plurality of trunk circuits and a pluralityof switching apparatus related in tandem, an improved arrangementincluding timing equipment in the trunk circuits for bringing aboutautomatic release of the associated switching apparatus under certainoperating conditions.

Afurther object of the invention is to provide in a trunk circuit,including'two incoming trunks, an improved arrangement whereby, a tonetest is performed when one of the incoming trunks is employed and areverse battery control is performedwhen the other of the incomingtrunks is employed.

Further features of the invention pertain to the particular arrangementof the circuit ele- Claims. (0!. 17-9-18) ments of thesystem, wherebythe above-outlined and additional operating features thereof :are at-'tained.

Sect. 1.T'he general arrangement of-the telephone system the telephonesystem, which apparatus has embodied therein the features of theinvention as briefly outlined above. Specifically, inorder to form 'aunified diagram, Figs. 2 to 9, inclusive, should be arranged verticallyin side-by-sideirelation from left to right, and Figs. 10 to14,-inelusive, should be-arranged vertically in side-byside relationfrom left to right and disposed -r.espectivelybelow Figs. 5*to9,inclusive.

More particularly, Fig. 2 illustrates the detailsof one of the toll linecircuits incorporated in the toll oflice; Figs. 2 to4, inclusive,illustrate the details of one of the toll circuits incorporated in thetandem ofiice; Figs. 5 and 6 illustrate the details of the repeater andtrunk selector incorporated in the tandem officepFigs. 10 and 11illustrate the details of one of the trunk circuits incorporated in thetandem oflice; Figs. '7 to -9, inclusive, illustrate the details of atrunk circuit incorporated in the sub-ofiice; Figs. 12andl3illustratethe details of one of a-group of trunk cirarea comprising atoll oflice ID, a magneto .ofiice 20, a tandem office30 and a sub-office40, the toll,

oflicel 0 being .disposedrelatively remote from the tandem oflice 30,and the tandem oflice 30 being disposed relatively near to themagnetoofiice .20

.and to the sub-office 40. The toll office l0 serves subscribersubstations of any suitable type and comprises a manual dial switchboard200; while the magneto office 20 serves subscriber substations of themagneto-type and comprises a manual .dial switchboard 28.6. The tandemoffice 30 "is. a

relatively small office of the automatic type, serving a number ofdifferent groups of subscriber substations rendered diiierent classes ofservice and at least one group of paystations. One of the groups ofsubscriber substations includes the subscriber substation TI. Also, thesubofficeAU is a relatively small ofiice of the automatic type serving agroup of subscriber substations, including the subscriber substation T2.

The toll oillce I and the tandem ofiice 30 are interconnected by a smallgroup of toll lines;

which group may comprise three individual toll 1 lines, including thetoll line 220. The magneto ofiice 20 and the tandem oifice *30 areinterconnected by a small group of trunk lines; which group may comprisethree individual trunk lines,

including the trunk line 280. The tandem office 30 and the sub-oflice 40are interconnected by a single trunk line 600; and also by a small groupof trunks; which group may comprise two individual trunks, including thetrunk H90. Each of the toll lines 220, etc., terminates in toll linecircuits respectively disposed in the toll office I0 and in the tandemoiiice 30, the toll line 220 terminating in the toll line circuits 2H)and 250 respectively disposed in the toll office I0 and in the tandemoifice 30. Each of the trunk lines 280, etc., terminates in trunk linecircuits respectively disposed in the magneto office 20 and in thetandem ofiice 30, the trunk line 280 terminating in the trunk linecircuits'285 and 28I respectively disposed. in the magneto ofilce 20 andin the tandem ofiice 3'0. terminates in a repeater and trunk selector500 disposed in the tandem ofiice 30 and in a trunk line circuit I00disposed in the sub-ofiice 40. Finally, each of the trunks II90, etc.,terminates in trunk circuits respectively disposed in the tandem office'30 and in the sub-oilice 40, the trunk I I90 terminating in the trunkcircuits I000 and 1200 respectively disposed in the tandem office 30 andin the sub-office 40. In the toll office I0, each of the toll linecircuits 200, etc., is accessible to the switchboard 200; and in themagneto office 20, each of the trunk line circuits 28 5, etc., isaccessible to the switchboard 286.

The tandem office 30 also comprises automatic switching apparatusincluding a plurality of finder-connector links 390, etc., provided withan associated distributor 388 and two incoming connectors 300, etc.,respectively individually associated with the trunk circuits I000 etc.,'the trunk circuit I000 being connected to the individually associatedincoming connector 300 by a trunk II'80. Each toll line circuit 250,etc., is provided with a line circuit individual thereto, the toll linecircuit 250 being provided with the line circuit 384 individuallyconnected thereto by the trunk 380. Also each trunk line circuit 281,

etc., is provided with a line circuit individual thereto, the trunk linecircuit 281 being provided with the. line circuit 385 individuallyconnected thereto by the trunk 283, Finally, each subscriber substationis provided with a line circuit individual thereto connected to theassociated subscriber line, the subscriber substation T I being providedwith the line circuit 3'81 individually connected to the associatedsubscriber line 386. The various line circuits 380, 38-5, 301, etc., arerespectively connected to the distributor 388 and are accessible to thefinders of the various links 390, etc. Each toll line circuit 250, etc.,is provided with two incomingtrunks, the toll line circuit 250 beingprovided with the two incoming trunks 470 and 480; and each trunk linecircuit I ZBI, etc., is provided with an incomingtrunk, the

The trunk line 600 trunk line circuit ZBI being provided with theincoming trunk 35. Also the repeater and trunk selector 500 is providedwith an incoming trunk 490; and each of the trunk circuits I000, etc.,is provided with an incoming trunk, the trunk circuit I000 beingprovided with the incoming trunk 400. The incoming trunks 4'80, etc.,extending to the toll line circuits 250, etc.,

are accessible to the repeater and trunk selector 500 and to the twoincoming connectors 300, etc.; while the trunks 410, etc., extending tothe toll line circuits 250, etc., are accessible to the connectors ofthe various links 390, etc. The incoming trunks 35H, etc., extending tothe trunk line circuits 281, etc. are accessible both to the connectorsof the links 390, etc., and to the two incoming connectors 300, etc. Thevarious subscriber lines 380, etc., are accessible to the connectors ofthe various links 390, etc., and to the two incoming connectors 300,etc. The incoming trunk 490 extending to the repeater and trunk selector500 is accessible to the connectorsof the various links 300, etc.; whilethe incoming trunks 400, etc., extending to'the trunk circuits I000,etc.- are accessible tothe connectors of the various links 390, etc.

The sub-oiiice 00 comprises automatic switching apparatus, including aplurality of finderconnector links 884, etc., provided with anassociated distributor 883; and an incomin con.- nector 385 individuallyassociated with the trunk line circuit E00 and connected theretoby thetrunk 800. Each trunk circuit I200, etc., is providedwith a line circuitindividual thereto, the trunk circuit I200 being provided with the linecircuit I10 individually connected thereto by the trunk I280. Eachsubscriber substation is provided with a line circuit individual theretoconnected to the associated subscriber line, the subscriber substation'I 2 being provided with the line circuit 882 individually connected tothe associated subscriber line 88I. The various line circuits I70, 882,etc., are respectively connected to the distributor 883 and areaccessible to the finders of the various links 004, etc. Each trunkcircuit I200, etc., is provided with an incoming trunk, the trunkcircuit I200 being provided with the incoming trunk I380; and the trunkline circuit is provided with an incomingtrunk 910. Also the sub-oflice50 comprises a trunk selector and digit sender I400 provided with anincoming trunk 890. The incoming trunks 1380, 910, 890, etc., areaccessible to the connectors of the various links 884, etc. while thetrunk selector and digit sender W400 has access to the incoming trunksI380, etc., extending to the trunk. circuits I200, etc. Finally, boththe connectors of the various links 804, etc., and the incomingconnector 005 have access to the various subscriber lines BBI, etc.

The line circuits 3'81, 802, etc., associated with the subscriber linesin the tandem ofiice 30 and in the suboifice 40 comprise facility forapplying battery potential over the control conductor of these lines tothe associated finders having ac cess thereto, as indicated at X inFigs. 3 and 8: while the line circuits, not shown, associated with thepaystation lines, not shown, in the tandem ofiice 30 and in thesubofiice 40 comprise the facility noted and additional facility forsuper- "imposing thereon an identifying tone, as indicated at Y in theline circuits 307 and 802 in Figs. 3 and 8. These arrangements, beingen? tirely conventional, are only indicated diagrammatically.

5 Scot. f2.--Th-e apparatus inoorpo'rcitedin, the

telephone sys'tem In the toll ofiicel,1.0,,theswitchboatdilifl isof theconventional jmanual .dial typalincluding cord tcircuitsnotshown. Eachof -.thejto1l:lin'e circuits :identical ,to the .;toll 'line circuit2li0; which comprises, as shown inQEigf ".2, ,a' relay roup including .asimplex ,pulsewrelayiltz I and aisignal relay R215, ,as well .ascarepeating :coil

.iIn themaeneto ,o'ince 20, .the switchboard .286 is of the conventionalmanual ,dial type and may". be identical .to the switchboard i200. .Similarly, the itrunkfline circuitsf2ii5, etc maybe identical to the.toll line circuit 210.

"In ,the'ltarfdem office, the tollline circuits 250,

etc,, ,and the 'trunliline circuits.r28l etc; may be identicalffthetollline circuit 150 comprises, as

a timer "4215, and "a relay group including-a "signal relay $12,230, asupervisory relayERMl], a dial relay R2150, a pulse relayRZfiOyan answer"relayR2T0,

-a switch relay R3 l0,v a control relay "R32 0, ;a line rela R330,ai-time --release:relayR3 '4'0, two hold relays R350, and R3 60, a*timerleaserelay R310,

a line relay fR'4l'0, :a timer relay R420, ia-seize relay R5 90, "a holdrelay RB- l0 ,a dial -relay'- R6 20, a cut-off "relay ;R63 0, an answerrelay R040, -a "supervisoryrelay R650, ;a start select relay $0555, asimplex -relay R560, a --ring-down relay -'-R065 and 'two -start relaysH.010 :and -R680.

The trunk circuits 1000, -etc., *are identical; and the ttrunk circuit1000 comprises, as shown in Figs. 10 and "1'1, a repeating -"coil ROI-11:5, a timer, :not :shown, :and a relay "group including a reversebattery 'relay R'IOHI, a cut-oifrelay 'Rt020,ia timer relayLRl030,"a:seizerelay1-Rl040,

a control relay "R 050, 'a dial relay :Ril 060,-a hold relayltlll'lllytwo line-relays RI'080 *and R511 [0, a supervisory relayR4120, 'a time release relay Rl1t30, an answer relay Rll14i0, ;a 'switchrelay R1150, a'hold relay 31160, and a sirnplexrelay .Also, .in thetandem office 30,"theline' circuits 384, 385 and 38'! may *be ofanygsuitable'types, while the distributor 388 is .of any conventionaltype. The subscriber substations 'Tl, etc,, are provided withconventional substation equipment; and ,the paystations, not shown, areof the conventional prepayment ;type. 1Further,'the private subscriber.lines lare provided with call registers .and .meters, not shown,Finally, the finder-connectonlinks .390, etc., are lof theistrowgetrestricted service :type disclosed in the -.copending V-application :of,Pier .Bakker, :Serial ,No. 723,525, -fi led .Janua1;y- 22, 1947; whileeach ,of the incoming connectors 4300, etc, is =of the Strowger type.and ,is substantially identical to the connector aportion or the=link.390. :Inpassing it-istnqtedthat the link 390 is of theimixedservice type and is responsive to the asingle-zdigits 7, 8, 9 and 0,respectively, to select the groups of trunks terminated in the first,second, third and fourth :levelsthereof ,and their automaticaliyitoioperate. .in order t,o;select an idle :trunk in the .previouslyselected V-group or leveL ,fAlso 'sponse to dialingtheidigitil.v

6 the linkT390- is=responsive to theiprefix' digits.2 or 3 iollowed.by.one of the digits.5, l6, 7,,8sand 9 to select .the respectivelycorrespon'ding fifth,

sixth, seventh, eighth .and nirithi. levels thereof,

terminating the lines extendingtothe subscriber substations andl..p.aystations. 'Thereaiter, the link 390 ,is responsive :to any thirddigitffrom Into ,0 touselect therespectively corresponding line in Zthe-.previously selected -level. Finally, the finder-connectorilinkjii'fi0,islresponsive to any fourth .digit'fromil to ojtoibring about codeineing of "the selectedflline I in the .event it is idle. The.,combination.o'f thefirst or prefix digit and thefourth code digitpermitsLthelink-"39'0ilto'rinjg the..called line with-any one.ofjtwenty'iindividual co'des; whereby ,aS -many as twenty party;sub,-scriber. substations may" be. arranged or any single partyline.

.fAlso'the link 390 comprisesa restricted service arrangement, wherebycertain of'the subscriber lines may not extend connections via 'th'eitwogroups of trunks "thatare respectively selected in response to dialingthe digits 'l and '9; and none cf the subscriber lines :may, extendconnections via 'theitrunks that "are "selected ;in re- In the sub-ofiice40,5the trunktline circuit-l0 0 comprises, ;as ,shown in "Figs. "7 8rand 9',-" a' repeating'coil RC'l60,,-a timer 936'and :a"relay groupincluding 'two ring-down relays R11 0 "and R120, a switch relay R130,:aline "relay R140, an answer relay "R750, a "hold relay R8 t0, asimplex relay R820, "a holdyrelay R030, *a time release "relay R84 0, adial relayRii 50, *a control "relay E860, fa line relay "R8l 0,--a'tonerelay RSt-Ogaseize relay R920, two 'startrelays R930 and R940, a timerrelay R950 and "a reverse battery-'relay RL'960." Also, thetrunk-circuits I"2 00,--etc.,are identical to the trunk circuit 1 000the 'tru'nk 'circuit 112 00 comprising, as shown'in Figs. 12 "and*1'3,"-a repeating "coil "-RCt2-l5, a =timer, not shown, and

a relay group including a reverse battery 'relay R10 1 0,'-a cut-'offrelay *R P32 0, a timer relay' R l3 30, a seize relay Rl040, a controlrelay R1350, --*a dial relay 13F360, *a hold relay Rt-310, two linerelays R0380 and R| -2-l 0,' a -supervisory relay R1220, a mime release-'relay R;| 2so, an a'nswer relay Ri -2'40, ---a switch relay l t/1 2.50, -a hold relay Rt260=anda simplex relay -Rt'Z-TO. i

-\lso %in the sub-o'fli'ce 40, the line circuits 17 0, 882, -e'tc.,'=may be of any suitable types; While the distributor 883 "is (of -anyconventional type. The subscriber substations T2 etc., are provided withconventional substation equipment; "while links 884, etc., :and the:incoming connector-8.85,

are of the conventional fitrowgertypes.

Finallyj'the trunk'selectonandzdigitsenderil400 comprises', as showniinFig. 14, a; relay group ineludingtwo' select-relays R; I 4-] 0 and :RI42:0,:a busy relay R0430, :a itest relay Rl4'40; a cutefoff relay Rl450,three pulse relays Rl4 8 5,- R;t455, and EH60, a shunt relay tR4410, aline irelay, R1415, a control relay T121480, and -a start relay R1490Also, the trunk selectorandadigit sender 1400 comprises asend switchI40! of therotary type, including two wipers 1-402 "and 1403 providedwith a magnetlvlil 1404 for 'drivingthe wipers nnte'd Stepmy-step in theclockwise "dire'ction 'away from their .home positions .with respect tothe associatedcon'tac'tlban'ks. -A better understanding of'theconnection'an'd arrangementof the. apparatusjiincorporatedinlthetelephonesystem willi'be jfacilitatecl'irom. .a considerationeof theextensionlof calls-involving the variousofiices.

. Sect. 3..Loca.l calls in the tandem oflice First assuming that a callis initiated at the subscriber substation TI in the tandem oflice 30that is to be completed locally to another subscriber substationtherein, the line circuit 381 is controlled via thQ'SllbSCIlbGl' line385 in order to govern operation I of the distributor 388; whereby anidle one of the links, such, for example, as the link 390 is assignedthereby. The finderof the assigned link 390 operates to find thesubscriber line 386 extending to the calling subscriber substation TI;whereby the line circuit 381 is operated in order to mark the subscriberline 386 as busy to the other links 390, etc. Also the connector ,of thelink 390 operates to return dial tone over the subscriber line 386to'the'calling subscriber substation TI; whereby the sub scriber at thecalling subscriber substation TI proceeds to dial the directory'numberof the called subscriber substation, which number might be 3654. Thefirst digit 3 received by the link 390 indicates that the present callis a local call and selects a portion of the ringing code. The connectorof the link 390. responds to the second digit 6 to select thecorresponding sixth level; and then responds to the third digit to'select the corresponding fifth line in the previously selected level;which line extendsto the called subscriber substation. The connector ofthe link 390 then responds to the fourth digit 4 to select the remainderof the ringing code that is to be employed to ring thecalled subscriberline. The first or prefix digit .3, in conjunction with the fourth digit4, selects one of twenty ringing codes at this time; whereby theparticular selected ringing code is projected over the called subscribedline in order to signal the corresponding one of the twenty partysubscriber substations connected to the called subscriber line, assumingthe called subscriber line is of the twenty party type and provided itis idle at this time. The operation. of the connector of the link 390 toreturn busy tone current to the calling subscriber substation TI in theevent the called subscriber line is busy is in accordance withconventional practice; and the remainder of the operation of theconnector of the link 390 in response to the answering of the call onthe called subscriber line, as well as the subsequent release of theestablished connection, are in accordance with conventional practice.

In view of the foregoing, it will be understood that a call from asubscriber substation in the tandemexchange may be completed locally toa paystation therein in an identical manner. Also, it will be understoodthat a call may be initiated at a paystation in the tandem exchage 30 bydepositing a coin or check thereat and then. subsequently completedlocally to a called'subscriber substation or paystation therein in aconventional manner.

Sect. 49A call from a subscriber substation or a paystation in thetandem ofl'ice to a subscriber substation in the sub-ofl'ice mannerpreviously explained. The subscriberat the calling subscriber substationTI then dials the prefix digit 9 followed by the director number of 8the called subscriber substation T2; which number might be 23; whereby.9-23 may be dialed. The connector of the link 390' responds to thedigit 9 to select the corresponding third level and then an idle trunkterminated therein, such, for example, as the trunk 400 extending to thetrunk circuit, I000, the trunk 400' being marked asidle' to theconnector of the link 390 by the absence of ground potential upon thecontrol conductor C403 thereof. When the connector of the link 390seizes the trunk 400, a loop circuit is completed for energizing inseries the windings of the line relays RI080 and RIIIO in the trunkcircuit I000j this loop circuit extending from ground potential by wayof the Winding of the line relay RI 080, the contacts I I34, the lowerlefthand winding of the repeating coil RCI I15 and the contacts I [GM tothe line conductor C402 of the trunk 400, and from battery potential byway of the winding of the line relay RI I I0, the con: tacts II52, theupper lefthand Winding of the repeating coil ROI I15 and the contacts I0I 2 to the line conductor C40I of the trunk 400. At this time the lineconductors CAM and C402 of the trunk 400 are connected togetherby wayof. the link 390 and the subscriberline 386 at the calling subscribersubstation TI. When this loop circuit is thus completed, both of theline relays RI080 and RIIIO operate. Upon operating,-the line relay RI II0, completes, at the contacts II I I, a circuit for operating the holdrelay RIO'I0. Upon operating, the hold relay RIO'I0 completes at thecontacts I013, a path, including the con-v tacts I I I3, for applyingbattery potential by way of the winding of the supervisory relay RII20to the simplex conductor CI IIB; which simplex conductor CI I16 isconnected by way of the upper and lower right-hand windings of therepeating coil RCI I15, the line conductors of the trunk H and the upperand lower left-hand windings of the repeating coil RCI2'I5 to thesimplex conductor CI2IB; which simplex conductor CI 216 is connected byway of the contacts I314 and I353 and the winding of the simplex relayRI2I0 in the trunk circuit I200 to ground potential. Accordingly, atthis time the winding of the supervisory relay RI I20 in the trunkcircuit I000 is energized in series with the winding of the simplexrelay RI2'I0 in the trunk circuit I200; whereby both the supervisoryrelay RI I20 and the simplex relay RI2'I0 operate. Also uponoperating,the hold relay RI 010 in the trunk circuit I000 completes, at thecontacts I012, a circuit including the contacts I034, for operating thetime release relay RI I30. Upon operating, the time release relay RI I30completes, at the contacts H34, a path for applying ground potential tothe control conductor C403 of the trunk 400, thereby to mark the trunk400 as busy to the other links 390 etc, having access thereto. Also thetime release relay RII30 completes,'at the contacts H35, a path forapplying ground potential to the timer start conductor CI'I38 in orderto initiate operation of the associated timer, not shown. Further thetime release relay RI'I30 completes, at the contacts I I31, a path,including the contacts [MI and I032, for applying battery potential byway of the winding of the timer relay RI030 to the timer conductorCI024; how-' ever, the timer relay RI 030 is not operated at this time.

Upon operating the simplex relay RI2'I0 in the trunk circuitI200completes, at the contacts I213, a circuit for operating the holdrelay RI260. Upon operating, the hold 'relay RI-260 completes,"

atthe contacts I262, a circuit for operating the switch relay RI250 anda-multiple circuit for energizing the lower winding of the answer relayRI240. When the lower winding of the answer relay RI 24015thus'energized, it does not operate at this time. Upon operating. theswitch relay RI250 interrupts, at the contacts I252 and- I254, normalconnections between the windings of the line relays RI 2 I 0 and RI380and the upper righthand'winding and the lower right-hand winding,respectively, of the repeating coil RCI215; and completes, at thecontacts I25I'",;- I253, I255v and I256, a path, including the resistorI224 and the upper right-handwinding and the lower righthand winding ofthe repeating coil-RC I215, for bridging the upper winding of the answerrelay RI240 across the line conductors-C I 28I and-"C I 282 of the trunkI280 extending to the line circuit 110. Further, the switch relay RI 250"completes, at the contacts I259, a path, includingthe contacts 12 33,for applying ground potential to the'contr'ol conductor-CI'383-of thetrunk I380; thereby toy'mark the; trunk I380 as busy to'the variouslinks; 884, etc., having access thereto.

When the upper winding of the answer relay RI240 is thus. bridged acrossthe line conductors CI28I and CI282'of the trunk I280, it is'energized,but itis not poled to operate. Also, the line circuit 110 operatestocontrol the distributor 883; whereby-an idle oneiof the findercon'ne'ctor links, such,-;forexample; as the link 884-: is assigned'foruse at this time; The finder of-theli-nk 884jfinds the calling, trunkI280 marked bythe line circuit 110; whereby the'connector of 'the link884 is,-conditioned to,be responsive to digits received over the trunkI280;

When thesubscriber at, the callingsubscriber substation TI dials thefirst digit 2, of the directory; number of thecalled subscribersubstation T2, the line relays RI 080- and RI I I0,in'the trunk circuit.I000 follow. Each time the line'relay RI I I0 restores and thenreoperates, .it; interrupts and then recompletes; at the contacts IIII,the previously mentioned circuit for. maintaining operated'the holdrelayRI010; whereby the lat. terrelay. remains operated during:impulsing.v as it; is of the slow-to-releasetype. Also each time the:linerelay; R I I, I 0. restores and then reoperates,

it completes. and then interrupts, at: the contacts II I2, a circuit,including the contacts I022 and thelatter relay operatesand remainsoperated during impulsing as it is of the slow-to-rel'ease type.Uponiop.erating,.the dialrelaylRI060 coinpletes, at the contacts I063, apath, including the contacts I 01I, for connecting theres'istor I025 inshunt. to: the windingof the linerelay: R1080 in order to: improveimpulsing over the loop circuit extending back to the calling subscribersubstation TI. Also the dial relay RI050: completes, at the contactsI065, a path, including. the contacts I I36; for "connecting theresistor' I I25 in shunt to the winding of the supervisory relay RI I20in order to improve inpulsing over the simplex conductor CII16.: Alsoeach time the line. relay RI I I0;restores1and then reoperates, itinterrupts and then recompletes, at the contacts III3.,..the previouslytraced circuit for energizinginseries the winding of thesupervisoryrelayRH20in the trunk circuit I 000- and the winding of thesimplex rel'ay R1210 in the trunk circuit I200; whereby therelaysmentioned follow; following by. the supervisory, relay RI I20 in thetrunk circuit I000 being without effect. a, w

The. first-time the simplex relay-"RI-210 111113118 .I,I32, foroperating the dial relayi RI 060; whereby thereby to retain operated thelink 8B4;

trunk circuit I200 restores and then reoperates,

it completes and then interrupts, at the contacts trunk -I 280, forenergizing in series the up'per' and lower windings thereof. Also eachtime the simplex'relay R1210; restores and then reoperates, itinterrupts and then recompletes, at the contacts I213, the previouslymentioned circuit for maintaining operated the hold relay RI260; wherebythe latter relayremains operated during impulsing asit is oftheslow-to-release type. Also, each time the simplex relay R-I210restores and then reoperates,-it completes and then interrupts, at thecontacts I212, a circuit, including the contacts I264 and I-24I, foroperating-the dial relay RI360; wherebythe latter relay operatesandremains operated duringimpulsing as it is of the slow-to-releasetype. Upon operating the dial relay Rl'360completes, at the contacts I36I, a path, includingtheresistor I223 and the contacts I26I, I21-I andI2-5I, across-the line conductors CI28I and-(H282 of -the -trunk- I280;thereby to improve impulsing over the trunk- I280 and the line circuittotheconnector of'the link; 884. Finally, each time the simplexrelay RI210restores and then reoperates, it interrupts and then recompletes, at thecontacts I21 I, the previously traced pathacross the line conductorsCI28I andCI282 of-the trunk I280; whereby the impulses of the seconddigit ;2--are transmitted over the trunk I280 and-the line circuit 110tothe connector of the link 884'in order to effect corresponding operationthereof. r

, Atathe conclusion of the second digit 2 dialed --at thecallingsubscriber substation TI, the line relays R I080and RII I0 in thetrunkcircuit-I000 remai-noperated; whereby the hold relay RI010isretained in its-operated position and shortly thereafter the dialrelay RI080 restores. Upon restoring;the dial:v relay R I0601 removesthe resisters I025. and II'25 from across the winding ofgthe line relayR1080 and the-winding of the supervisory relay RI 120, respectively.Also at this time the winding of the supervisory relay B11 20 in thetrunk circuit I000-and the winding of'the simplex relay R1210 in thetrunk circuit I200 are steadily energized inseries circuit relation;whereby therela-ys mentioned are retained 'in' their operated positions.I v

flf heoperated simplex'relay RI'2-10 in the trunk circuit I200 retainsoperated the hold relay R4260 and effects restoration of the dial relayRI360: shortly thereafter, si-ncethe latter relay isof. theslow---to-release type. Upon restoring the dial relay RI 360 interrupts,at" the contacts I-3-6I, the previously traced path forconnectingtheresistor l-2 23 across the line conductors CI28I and; Cl282of the trunk I280; whereby the upper winding of I the answer relay RI240no longer--short-circuited by the resistor I223. Also upon restoring,-the dial relay RI 360" completes, at the contacts; I364,,a holdingcircuit, including thecontacts I342-, I34I, I251 and I-262, forenergizi'ng inseriegthe upper and lower windings oi the, seize relayRI340; and a multiple path, also including the. contacts I 258; forapplying ground potential in the trunk circuit I200to the controlconductor CI283 of the trunk I280,

ace-7,854 V "In view of the foregoing explanation of'the manner in whichthe second digit 2 dialed at the calling subscriber substation TI isreceived by the trunk circuit I009, and repeated therefrom over-thetrunk I I9!) to the trunk circuit- I200 and then repeated therefromtothe connectorof the link 88 1, it will be understood that the thirddigit 3'dia1ed at the calling subscriber substation TI istransmitted inan identical manner to the connector of the link 884. The connectorofthe link Iss4 "responds to the digits 2 and 3' to select the subscriberline 88I extending to the called subscriber substation T2; 7 Thesubsequent operation of the connector of the link 884 depends uponthe-idle r busy condition of the calledsubscriber substation T2 at thistime; and in the event the called subscriber substation T2 is busy atthis time, the connector of the'link 88:3 operatesin order to returnbusy tone current over the truhk'IZSdto the-trunk circuit I280; which"busy tone current traversing the upper righthand winding and the lowerright-hand winding of the repeating coil RCI215 induces a correspondingbusy tone current in the left-hand windings thereof. The busy tonecurrent is returned over the trunk H90 and traversing the righthandwindings of the repeating coil RCI I induces a'corresponding busytone current in the upperleft-handwinding and the lower left-handwinding thereof; which busy tone current is returned over the loopcircuit to the calling sub=- scriber substation 'II in order to indicateto the subscriber thereat that the desired connection cannot be had atthis time by virtue ofthe busy condition of the calledsubscribersubstation T2.

On the other hand, in the event the called subscriber substation T2 isidle at this-time,- "ringing 'ciu're'nt is projected from the connectorof 12 *Upon restoring, the supervisory relay Ri I the trunk circuit I900completes, at the contacts II2I, a circuit, including the contactsit'll, I062 and II3I, for energizing thewinding'of the cutofi'relayRI020, and a'multiple circuit, also including the contacts I03I, forenergizing the the link 884 over the subscriber line 88Ithereto and theline circuit 882 is operated inorder to mark the subscriber line BSI asbusy to the other links 884, etc., having access thereto. Also, ringbacktone current is returned from the connector of the link 884 over thepreviously traced connection to the calling subscriber substation TI inorder to indicate to the subscriber thereat that the called subscribersubstation T2 is being rung.

When the subscriber at the called subscriber substation T2 answers thecall, the connector of the link 884 operates in order to reverse thepolarity of the trunk I280; whereby the upper winding of the answerrelay RI240 is poled to operate. Upon operating, the answer relay RI246completes, at the contacts I242, acircuit for energizing the upperwinding of the control relay RI350; whereby the latter relay operatesUpon operating the control relay R'I350 completes, at the contacts I354a holding circuit,

including the contacts-|222 and I250 and the resistor I225 forenergizing the winding of the simplex relay RI210; interrupts, at thecontacts 1353, the previously traced original path for in the trunkcircuit I000; whereby the supervisory relay RI220 isretained in itsrestored'position and the supervisory relay RI I20 restores.

Winding of the reverse battery relay RHHU; whereby the cut-ofi -relayRI020 and the reverse battery relay RIEIIll'operateshortly thereafter,bother" these relays being of the slovw-to- -o'perate type." Uponoperating'the cut-off relay R1020 interrupts, at the contacts I02I; thepreviously traced connection between the Winding'of the timer relayRI630 and the timer conductor CI 02 1, thereby positively to preventoperation of the timer relay RIilBil under the control of the associatedtimer, not shown." Upon operatingfthe reverse battery relay RIGIDcompletes, at the contacts IOI5, a holding circuit for energizing thewinding thereof, and -including-the contacts 3|, I I2I, I062 and I0.Alsothe reverse battery relay RIIJII) reverses, at the contacts IOII,IOI2, IOI3 and IBM; the polarity of the trunk dilil'with respect to theline relays RI 080 and RI I I0; which reversal of polarity overthe trunk290 and the link 39!! is effective to operate a meter, not shown,individually associated with the calling subscriber substation -'II orotherwise to assess a charge against the calling subscriber substationTI. At this time an established connection is completed between thecalling subscriber substation TI in the tandem ofiice 30 andthecalled'subscriber substation'TZ in the sub-office d0.

At-the conclusion of the established connec tion, when the subscriber atthe called subscriber substation T2 disconnects, theco'nnectoricf thelink 884 is operated in order again to reverse the polarity of the trunkI280; whereby the answer relay 'Ri2d0 in the trunk circuit I200 ispoleclto ously tracedlholding circuit for maintaining operated thesimplexrelayRIZl'Il; and recom'plet'es,

at .the contacts I353; the previously traced original' path for applyingground potential byway of the winding of the simplex'relay RI210 to thesimplex conductor CIZTG.

Accordingly, at this time, the Windin of the-simplex relay RI210 'in thetrunk circuit I 200 islagain energized in series with the winding of thesupervisory. relay RI I20 in the trunk circuit I060; whereby the simplexrelay RI210 is retained in its operated position and the supervisoryrelay RI I20 reoperates.

Upon reoperating, the supervisory relay RI I20 interrupts, at thecontacts II2I, the previously traced circuits 'for maintaining operatedthe cutoff relay RI020 I and the reverse battery relay RIOI0. Uponrestoring, the reverse battery relay RIIIIO again reverses, at thecontacts I0; I042, IOI3 and IOI i, thepolarityof thetrun'k llflilwithrespect to the line reIaysRIIlSO-and RI I It in the trunk circuit I 000;however without efiect at-this time. Up on restoringythe cut-01frelay'RIllzfi again; completes-, a't the contacts i021, the previouslytraced connection between the; winding of the timerrelay RI030and-theiimercongluctor CI 0-24 extending to the timer, not shown; where-

